Silent chain with improved rocker joint

ABSTRACT

A silent chain of the rocker type has groups of links joined together at joints by pins extending through openings at the ends of the links. At each joint one pin is wedged in the openings in one group of links and another pin, in rocking engagement with the first pin, is wedged in the openings in the adjacent group of links. The openings and the pins have complementary substantially straight wedging surfaces converging as they extend outwardly from the center of the openings. The aligned openings of two adjacent groups of links define a channel at each joint which is substantially filled by the two pins at that joint.

Avramidis 1 SILENT CHAIN WITI-I IMPROVED ROCKER JOINT [75] Inventor:Stellios Antony Avramidis,

. Greenfield, Ind.

[52] US. Cl 74/25l S, 74/253 S [51] Int. Cl. Fl6g 13/02 [58] Field ofSearch 74/253 S, 254, 251 S,

[56] References Cited UNITED STATES PATENTS 2,669,879 2/1954 Pierce74/253 S 2,643,485 9/1953 MacArthur.... 74/253 S 3,540,302 11/1970Bendall. 74/254 X 1451 July .3, 1973 3,535,871 10/1970 Jefi'rey 74/250 SX Primary Examiner -Leonard H. Gerin Attorney-F. W. Anderson, C. E.Tripp and J. F.

Verhoeven 57 ABSTRACT A silent chain of the rocker type has groups oflinks joined together at joints by pins extending through openings atthe ends of the links. At each joint one pin is wedged in the openingsin one group of links and another pin, in rocking engagement with thefirst pin, is wedged in the openings in the adjacent group of links. Theopenings and the pins have complementary substantially straight wedgingsurfaces converging as they extend outwardly from the center of theopenings. The aligned openings of two adjacent groups of links define achannel at each joint which is substantially filled by the two pins atthat joint.

6 Claims, 7 Drawing Figures PATENTEU JUL 3 I975 Sim-1N4 INVENTOR.STELLIOS ANTCIUY AVRAIIDIS AT TORNFYS SILENT CHAIN WITH IMPROVED ROCKERJOINT BACKGROUND OF THE INVENTION 1. Field of the Invention Thisapplication relates to silent chains of the rocker joint type and moreparticularly to an improved chain of superior strength to reduce theelongation thereof when under tension.

2. Description of the Prior Art Silent chains, as distinguished fromroller type chains, have teeth which engage the teeth of the sprocket onwhich the chain is received. A typical rocker joint type of silent chainhas adjacent sets of links joined by a pair of pins. One of the pins issecured in openings in one of the groups of links and the other pin issecured in openings inthe other group of links. Both pins pass throughthe openings in both sets of links, and both pins have arcuate faces forrocking engagement to render the chain flexible. Typical silent chainsof the rocker joint type are shown in the patents of Howe U.S. Pat. No.1,188,657; Morse U.S. Pat. No. 1,634,334; Belcher U.S. Pat. No.1,644,656; Rothman U.S. Pat. No. 1,822,749; and Terepin U.S. Pat. No.3,213,699.

Some of these rocker type silent chains will yield, or give, slightlyunder tension so that shock, or a sudden application of load,-will notfracture the chain. For example, in the chain shown in Rothman U.S. Pat.No. 1,822,749, flexible, curved pins are used which flattenslightlyunder load and shock to provide elasticity to the chain. Thereare, however, applications where elasticity in the chain is not requiredor desired, as, for example, in uses where pitch changes because of wearor stretch must be minimal.

There are also applications where maximum strength, for any givenchain-size, is desirable.

SUMMARY OF THE INVENTION The silent rocker joint type chain of thepresent invention is strong, inelastic, and especially resistant towearfThe chain, like the typical silent chain of the rocker joint type,has groups of aligned links which are joined to adjacent groups of likelinks by'pairs of pins. As is conventional in this type of chain, thepins have facing arcuate surfaces for engagement as the groups of linkspivot with respect to each other about the pins during flexing of thechain. In the preferred form of the present invention, however, theopenings at the ends of the links of each group in which the pins arereceived to connect adjacent groups have upper and lower straightconverging wedging surfaces. Oneof the pins at each joint is received inthe aligned openings of one group of links. The pin has upper and lowerstraight converging wedging surfaces complementary to the wedgingsurfaces of the openings so that the pin is wedged tightly into theopenings of the group when tension is applied to the chain. The otherpin at that joint is received in the openings of the adjacent group oflinks, and the other pin of that joint is wedged between upper and lowerstraight converging wedging surfaces of the openings of the adjacentgroup of links. As in conventional silent chain of the rocker jointtype, both pins passed through openings of both connected groups, but,in the present invention, the two pins substantially fill the channeldefined by the aligned openings of the two groups of links.

For any given size chain, and any given size chain link, the larger theopenings at the ends of the links, the weaker the linkends will be, and,under high fluctuating loads, the greater will be the elasticity of thechain and the greater will be the likelihood for link failure.Similarly, the smaller and thinner the pins, the greater the flexure ofthe pins under high fluctuating loads and the greater the elasticity ofthe chain as well as the greater the possibility of pins shearing. Inthechain of the present invention, however, the opening is not so large asto weaken the link ends and the pins are not so small as to flex underload, because the pins are large enough (and the openings small enough)that the pins substantially fill the channel defined by the alignedopenings of two adjacent groups. The pins have 'no notches, and thegeometry of the pin allows the most efficient use of the space in whichthe pin is located. This results in smaller pin diameters which requiresmaller link openings to improve the strength of the link.

Each pin of the chain of the present invention is wedged tightly into agroup of links when the chain is under tension to minimize wear, andhence elongation, of the chain from long and severe use. The pins may bedesigned to create a press fit in the openings. Preferably, a smallclearance is left behind eachpin so that each pin will. seat tightlybetween the upper and lower wedging surfaces, and not against the outeredge of the opening.

It is therefore one object of the present invention to provide a silentchain of the rocker joint type in which there is minimum wear betweenthe pins and the links.

It is another object of the present invention to provide an inelasticsilent chain of the rocker joint type.

It is another object of the present invention to provide a rocker jointtype chain of maximum strength for a given size.

. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in perspective ofthe chain of the present invention mounted on sprockets. I

FIG. 2 is a plan view of the chain of FIG. 1 with portions being brokenaway.

perspective of the rocker joint type of the present invention mounted onsprockets l2, 14. The chain has a plurality of groups of links GA, GB(FIG. 2) which are connected together bypairs of pins P1, P2 at jointsJ.

As shown best in FIG. 2, every other group of inks (groups GA) consistofinner links 16a while alternate groups of links (groups GB) consist ofinner links 16b and outer links 18. For illustrative purposes only, thegroup of links GA consist of a plurality of spaced lateral aligned innerlinks 16a which extend, at each end, into meshing relationship with thelinks of groups GB. The links of groups GB consist of a plurality ofspaced laterally aligned inner links 16b bounded, at each side, by anouter link 18. The links of all the groups GB extend into intermeshingrelationship at each end with the links of the groups GA. It will beunderstood that other arrangements of links could be utilized, insofaras the present invention is concerned. For example, the links of eachgroup could be divided into sets of two or more contiguous links witheach set spaced from adjacent sets to receive sets of links of adjacentgroups of links in intermeshing relationship.

As shown best in FIGS. 3 and 4, each inner link (16a and 16b) has anopening 20 at one end and an opening 22 at the opposite end. Since theopenings are identical, except of opposite hand, only the opening 20will be described. As shown best in FIG. 6, the inner segment 24 of theopening (that is, the segment on the side toward the center of the link)lies on a circle C and extends for approximately 150 about the center Mof the circle, which, for convenience of description, may be referred toas the center of the opening.

An imaginery line N extending between the center of opening 20 and thecenter of opening 22 will be considered a longitudinal axis of the linkfor convenience of description. The longitudinal direction will beconsidered parallel to axis N and lateral direction will be consideredperpendicular thereto. Extending outwardly from the ends of the circularare 24 are a straight wall section, or boundary, 26 on one side of axisN, and a straight wall section, or boundary, 28 on the opposite side ofsaid boundary. These two wall sections, which extend, by way of example,in directions approximately 45 apart, converge (without meeting) as theyextend toward the outer side of the link. It will be understood -thatthis angle .is given by. way of illustration, since other angles couldbe used between the converging wall 1 sections. The wall segmentsterminate at the ends of the outer segment 30 of the opening, which is acircular are lying on circle C. Thus, the opening 20 has inner and outercircular segments lying on a circle C, and two wall segments on oppositesides of the axis N define straight chords of the circle C whichconverge (without meeting) toward the outer side of the opening.

As shown best in FIG. 3, the openings 20 at one end of the links ofgroup GA are aligned with the openings 22 of the links of group GB, andthe openings 22 at the opposite end of the links ofgroup GA are alignedwith the openings 20 of the links of another group GB. At each end ofeach group of links in the chain, there is a channel 32 extendingthrough all the links defined by the openings 20 in every other link andthe openings 22 in alternate links. Stated another way, each channel 32is defined by the openings 20 in one group of links (say group GA) andthe openings 22 in the other, adjacent, group GB of links.

It will be noted, from FIG. 3, that each channel has two straightoppositely sloping wall segments on one side of the longitudinal axes ofthe links, two straight oppositely sloping wall segments on the oppositeside of the longitudinal axes of the links, and two circular sidesegments, intersecting said longitudinal axes. The wall segments on eachside of the channel 32 converge (without meeting) as they extend awayfrom the center of the channel. In other words, opposing wall segmentsof the channel are inclined to diminish the lateral span S of thechannel toward the outer edges OE of the channel.

Each channel receives two pins, P1 and P2. As shown best in FIGS. 2 and7, the pin P1 extends through all the links of both groups of links GAand GB at the chain joint defined by the pins except the two outer links18 of group GB. The pin P2 extends through all the links of both groupsof links GA and GB at the joint including the two outer links 18 ofgroup GB. The outer links 18, as shown in FIG. 5, have reduced openings33a and 3317 which are similar but of opposite hand. The pins P2 aretightly received in these openings. It will be noted that although theshape of link 18 is substantially similar to the shape of links 16a and1611, the link is oriented upside down relative to the other links. Asshown best in FIG. 1, this is done so that the links 18 act as guidelinks to keep the chain on the sprockets. It will be understood that adifferently shaped link, such as an oval link, could be used as a guidelink.

As shown best in FIG. 3, the pin Pl has opposite straight walls, 34 and36 respectively, which converge (without meeting) at an angle equal tothe angle of convergence of the opposing wall segments of the opening20, and which are therefore complementary thereto. The pin P1 is alsocomplementary to the converging walls of opening 22. The pins P2 havesimilar walls, 38, 40 which are complementary to the opposing straightconverging walls of the openings 20 and 22. The pins P1 are secured,when the chain is under tension, by wedging action in openings 20 and 22of all the links of group GA; the pins P2 are secured, when the chain isunder tension, by wedging action in openings 22 and 20 of all the linksof group GB. The pins P1 and P2 all have arcuate surfaces 42, 44 forrocking engagement when the chain flexes at the joint. The pins may beslightly over size to fit into the openings by a press fit.

It will be noted from FIG. 3 that when the chain is under tension andthe group GA of links is pulled away from the group GB of links, bothpins at the joint between the links are urged outwardly with respect tothe group of links into which they are wedged, to hold the pins tightlyagainst rubbing action with that group of links. There is a slightclearance 46 behind each pin and the outer wall of the opening intowhich the pin is wedged to eliminate the possibility of the pin seatingon the outer surface instead of seating on the wedging surfaces of theopening. Although the pins pass through the other group of links (thatis, the group in which they are not wedged), they do not normallycontact that other group of links. Thus, when the chain is undertension, the pins are wedged, by means of straight, relatively shallow,sloping, complementary wedging surfaces on pin and opening, againstrubbing action in the opening. The pins rock against each other, as inconventional rocker joint type silent chain, to permit flexure of thechain.

It is significant to note that in the present invention, the two pins ateach joint substantially fill the channel through the openings in bothgroups of links. This is important to add strength, rigidity, andinelasticity to the chain. Since substantially all of the channel isused for the pins, without any significant wasted space, the openingsare as small as possible (to strengthen the links) and the pins are aslarge as possible (to strengthen the joint). The pins do not flexsignificantly under tension in the chain, and the ends of the links donot yield under such tension. Instead, a rigid, strong chain, withoutsignificant elasticity or stretch, is provided. Because the pins arewedged between relatively shallow angled walls, the pins are firmly heldagainst rubbing in the opening.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

What is claimed is:

l. A silent chain having a plurality of groups of links with sprocketengaging teeth, said links having openings at each end, the openings atone end of one group of links aligned with the openings at the oppositeend of the adjacent group of links, said aligned openings defining achannel having opposing boundaries each defined by both said one groupof links and said adjacent group of links, at least one of saidboundaries defined by two substantially straight elongated wedgingsurfaces inclined to diminish the lateral span of the channel towardsthe outer edges of the channel, and a pair of pins and only a pair ofpins received in said channel, said pins having arcuate facing surfacesfor rocking engagement and having opposite surfaces for engagement withthe opposing boundaries of the channel, said opposite pin surfacesextending substantially the full width of the pin and beingcomplementary to the opposing channel boundaries for wedging engagementtherewith, said pins substantially filling the channel when in rockingengagement.

2. A silent chain having a plurality of groups of links with sprocketengaging teeth, said links having openings at each end, the openings atone end of one group of links aligned with the openings at the oppositeend of the adjacent group of links, said aligned openings defining achannel having opposing boundaries each defined by both said one groupof links and said adjacent group of links, both of said boundariesdefined by two substantially straight elongated wedging surfacesinclined to diminish the lateral span of the channel towards the outeredges of the channel, and a pair of pins and only a pair of pinsreceived in said channel, said pins having arcuate facing surfaces forrocking engagement and each having substantially straight opposingsurfaces extending substantially the full width of the pin forengagement with one side of the opposing surfaces of said channel, saidopposing pin surfaces being complementary to the opposing channelboundaries for wedging engagement therewith, said pins substantiallyfilling the channel when in rocking engagement.

3. A silent chain having a plurality of groups of links with sprocketengaging teeth, each group of links having openings at each end, each ofsaid openings having substantially straight, elongated convergingopposing walls, the openings at one end of each group of links alignedwith the openings at the opposite end of the adjacent group of links todefine a channel with the opposing walls of one group of linksconverging oppositely to the opposing walls of the adjacent group, saidwalls converging as they extend outwardly from the center of thechannel, a first pin received through openings of both of said groups oflinks, said first pin having converging substantially straight opposingwalls extending substantially the full width of the pin to be receivedtightly between the converging walls of the openings in one of saidgroup of links, a second pin received through openings of both of saidgroups of links, said second pin having converging substantiallystraight opposing walls extending substantially the full width of thepin to be received tightly between the converging walls of the openingsin the adjacent group of links, said pins having facing arcuate surfacesfor rocking engagement, said first and second pins alone received insaid channel and said pins substantially filling the span between theouter edges of the channels.

4. The mechanism of claim 1 in which each of said openings comprisesopposite arcuate segments and opposite sloping straight segments. I

5. The mechanism of claim 2 in which a clearance is provided between theouter edge of the link opening and the outer edge of a pin wedgedtherein.

6. The mechanism of claim 3 including outer links for of said pins.

1. A silent chain having a plurality of groups of links with sprocketengaging teeth, said links having openings at each end, the openings atone end of one group of links aligned with the openings at the oppositeend of the adjacent group of links, said aligned openings defining achannel having opposing boundaries each defined by both said one groupof links and said adjacent group of links, at least one of saidboundaries defined by two substantially straight elongated wedgingsurfaces inclined to diminish the lateral span of the channel towardsthe outer edges of the channel, and a pair of pins and only a pair ofpins received in said channel, said pins having arcuate facing surfaceSfor rocking engagement and having opposite surfaces for engagement withthe opposing boundaries of the channel, said opposite pin surfacesextending substantially the full width of the pin and beingcomplementary to the opposing channel boundaries for wedging engagementtherewith, said pins substantially filling the channel when in rockingengagement.
 2. A silent chain having a plurality of groups of links withsprocket engaging teeth, said links having openings at each end, theopenings at one end of one group of links aligned with the openings atthe opposite end of the adjacent group of links, said aligned openingsdefining a channel having opposing boundaries each defined by both saidone group of links and said adjacent group of links, both of saidboundaries defined by two substantially straight elongated wedgingsurfaces inclined to diminish the lateral span of the channel towardsthe outer edges of the channel, and a pair of pins and only a pair ofpins received in said channel, said pins having arcuate facing surfacesfor rocking engagement and each having substantially straight opposingsurfaces extending substantially the full width of the pin forengagement with one side of the opposing surfaces of said channel, saidopposing pin surfaces being complementary to the opposing channelboundaries for wedging engagement therewith, said pins substantiallyfilling the channel when in rocking engagement.
 3. A silent chain havinga plurality of groups of links with sprocket engaging teeth, each groupof links having openings at each end, each of said openings havingsubstantially straight, elongated converging opposing walls, theopenings at one end of each group of links aligned with the openings atthe opposite end of the adjacent group of links to define a channel withthe opposing walls of one group of links converging oppositely to theopposing walls of the adjacent group, said walls converging as theyextend outwardly from the center of the channel, a first pin receivedthrough openings of both of said groups of links, said first pin havingconverging substantially straight opposing walls extending substantiallythe full width of the pin to be received tightly between the convergingwalls of the openings in one of said group of links, a second pinreceived through openings of both of said groups of links, said secondpin having converging substantially straight opposing walls extendingsubstantially the full width of the pin to be received tightly betweenthe converging walls of the openings in the adjacent group of links,said pins having facing arcuate surfaces for rocking engagement, saidfirst and second pins alone received in said channel and said pinssubstantially filling the span between the outer edges of the channels.4. The mechanism of claim 1 in which each of said openings comprisesopposite arcuate segments and opposite sloping straight segments.
 5. Themechanism of claim 2 in which a clearance is provided between the outeredge of the link opening and the outer edge of a pin wedged therein. 6.The mechanism of claim 3 including outer links for one of said groupsreceived tightly on the ends of one of said pins.